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CVE-2026-54399 — httpcore5

HIGHFix: apache/httpcomponents-core@d96a00f

CVE-2026-54399 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in org.apache.httpcomponents.core5:httpcore5. A fix is available for org.apache.httpcomponents.core5:httpcore5 — see the affected versions and patch details below.

Apache HttpComponents Core: Unbounded HTTP Header/Line Length in Default Configuration

Also known asGHSA-hf6x-8p5f-cgmf
Published
Updated
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed
Exploitation data as of Oct 2, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-54399.

EPSS Exploitation Probability

via FIRST.org ↗
0.9%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs57th percentile — riskier than 57% of all scored CVEsHighest risk
0.06%0.50%0.94%1.37%0.6%0.9%0.9%Aug 26Oct 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-54399 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 382,205 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

2 pkgs affected
☕org.apache.httpcomponents.core5:httpcore5☕org.apache.httpcomponents.core5:httpcore5

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

Uncontrolled Resource Consumption vulnerability in the HTTP/1.1 message parser in Apache HttpComponents Core (5.4.2 and earlier, 5.5-beta1 and earlier) allows an remote attacker to cause a denial of service through memory exhaustion by sending messages with excessive number of headers / excessive header length

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
☕Mavenorg.apache.httpcomponents.core5:httpcore5all versions5.4.3org.apache.httpcomponents.core5:httpcore5:5.4.3
☕Mavenorg.apache.httpcomponents.core5:httpcore5≥ 5.5-alpha1&&< 5.5-beta25.5-beta2org.apache.httpcomponents.core5:httpcore5:5.5-beta2

Affected Products

1 product · 3 configurations
Application
httpcomponents coreapache
≥ 5.0 && ≤ 5.4.2
1 version
5.5

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.httpcomponents.core5:httpcore5, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update org.apache.httpcomponents.core5:httpcore5 to 5.4.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-54399 is resolved across your whole dependency graph.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

Important: This flaw in Apache HttpComponents Core allows a remote attacker to cause a denial of service by sending HTTP/1.1 messages with an excessive number or length of headers. This can lead to memory exhaustion in applications using the affected HTTP/1.1 message parser, impacting service availability.

Workaround published by Red Hat
To mitigate this issue, configure an upstream proxy or web application firewall (WAF) to enforce limits on the number and length of HTTP headers. This prevents malformed requests from reaching and exhausting the vulnerable Apache HttpComponents Core component. Consult your proxy or WAF documentation for specific configuration. A service restart may be required for changes to take effect.
Source: Red Hat security advisory for CVE-2026-54399 (CC BY 4.0)
ProductFixed inAdvisory
Cryostat 4 on RHEL 9cryostat/cryostat-agent-init-rhel9:0.7.0-12RHSA-2026:68333
Red Hat build of Apache Camel 4.18.3 for Spring Boot 3.5.16httpcoreRHSA-2026:54622
Red Hat build of Quarkus 3.33.2.SP3see advisoryRHSA-2026:47172
OpenShift Developer Tools and Services 4.12ocp-tools-4/jenkins-rhel8:1786628667RHSA-2026:60247
OpenShift Developer Tools and Services 4.13ocp-tools-4/jenkins-rhel8:1786628681RHSA-2026:60249
OpenShift Developer Tools and Services 4.14ocp-tools-4/jenkins-rhel8:1786533561RHSA-2026:60248
OpenShift Developer Tools and Services 4.15ocp-tools-4/jenkins-rhel8:1786533565RHSA-2026:60239
OpenShift Developer Tools and Services 4.16ocp-tools-4/jenkins-rhel9:1787125166RHSA-2026:60251

Frequently Asked Questions

Uncontrolled Resource Consumption vulnerability in the HTTP/1.1 message parser in Apache HttpComponents Core (5.4.2 and earlier, 5.5-beta1 and earlier) allows an remote attacker to cause a denial of service through memory exhaustion by sending messages with excessive number of headers / excessive header length
O3 Security · Impact-Aware SCA

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CVE-2026-54399: httpcore5 — Fixed in 5.4.3 | O3 Security